Hi folks Having spent the last week hacking, I've found a common irritation, so I have a proposal to mitigate it. Of course, this issue may not bug anyone else, so I'm a little hesitant. In pessimal pedagogical order, the proposal: pattern synonyms. I want to be allowed to write stuff like P x y z = C x (y, [z]) defining a capitalised symbol with parameters used linearly in a pattern on the right-hand side. Pattern synonyms should be fully applied and expand macro-style wherever patterns or terms appear, hence should not give rise to cycles, just like type synonyms. It seems (and is) trivial. Why would it help? Well, it would help me, because I often write more complex types than strictly necessary to represent data in order to expose its structure and thus gain free equipment. For example, taking newtype Comp f g x = Comp (f (g x)) -- applicative if f and g are newtype Prod f g x = Prod (f x, g x) -- applicative if f and g are newtype Const x y = Const y -- applicative if x is a monoid newtype Id x = Id x -- trivially applicative newtype Any = Any Bool -- equipped with the disjunctive monoid structure all of which I keep lying around anyway, I might well write type MyEffect = Comp Maybe (Prod (Const Any) Id) which is the same as type MyEffect' x = Maybe (Bool, x) except that (1) MyEffect :: * -> * is an applicative functor without further ado (because it is composed from suitable components), hence I get lots of free kit for traversing data with it. (If you're interested, we use this to update terms where some variables have been changed and others have been deleted entirely: we want to know the new term if it exists, and whether it differs from the old one.) MyEffect' is meaningless. (2) Pattern matching on MyEffect x is much more annoying than on MyEffect' x. I want to write Bang :: MyEffect x Bang = Comp Nothing Bing :: x -> MyEffect x Bing x = Comp (Just (Prod (Any True), Id x)) Dull :: x -> MyEffect x Dull x = Comp (Just (Prod (Any False), Id x)) and have done with it. Does this happen to anyone else? Would pattern synonyms help? Thought I'd ask, anyway. All the best Conor